EP3086454B1

EP3086454B1 - Improving life of a semiconductor by reducing temperature changes therein via reactive power

Info

Publication number: EP3086454B1
Application number: EP16165712.7A
Authority: EP
Inventors: Robert Gregory Wagoner; David Smith
Original assignee: GE Energy Power Conversion Technology Ltd
Current assignee: GE Energy Power Conversion Technology Ltd
Priority date: 2015-04-22
Filing date: 2016-04-18
Publication date: 2020-02-19
Anticipated expiration: 2036-04-18
Also published as: CN106067680B; BR102016008250A2; CA2927275C; US20160315533A1; CN106067680A; US9859787B2; EP3086454A1; CA2927275A1

Description

FIELD OF INVENTION

The present invention relates generally to extending the useful life of a power semiconductor. More specifically, the present invention relates to extending the useful life of a semiconductor when operating as an electronic switch in renewable energy applications.

BACKGROUND OF THE INVENTION

Renewable energy, harvested from natural phenomena such as sunlight and wind, has replaced conventional fuels in areas of energy service and power generation. Electrical power devices, such as semiconductors, convert energy obtained from renewable energy sources, such as solar power and wind power, from dc or variable frequency ac to utility (grid) frequency. Conversion is generally achieved by switching a plurality of semiconductors on and off at high frequency to synthesize sine wave voltages via pulse width modulation (PWM) techniques.
Three-terminal semiconductors, such as insulated-gate bipolar transistor (IGBTs), metal-oxide-semiconductor field-effect transistors (MOSFETs), and thyristors are commonly used as switching devices in electrical applications. MOSFETs, used primarily in low voltage applications, may increase the current rating of a switch by placing several devices in parallel. Thyristors, used primarily in high voltage applications, require a finite time delay after the current in the thyristor has extinguished before the anode can again be positively biased and retain the thyristor in the off-state. IGBTs combine the performance in the on-state in high voltage devices with high impedance, thus making it a popular choice in power generation applications.
Transitioning each IGBT from the on-state to the off-state and vice versa results in heat production, as power is dissipated within each IGBT during switching events. The higher the current being switched on or off, the more losses, therefore the more heat. As current increases, the conduction losses within each IGBT also increase. Just as the power from renewable energy sources can often vary throughout a day, so can losses dissipated in the IGBTs. Therefore, the temperature of the IGBTs vary with changes in the output of the renewable energy sources. The thermal cycling, which may occur over minutes or hours, can result in mechanical stress and increased rates of IGBT failure over time due to material fatigue.
The life of an IGBT can be reduced due to thermal cycles. Thermal cycles, specifically in the baseplate and the bond wire of the switch, among others factors, results in device fatigue. Extreme changes between high and low temperatures decrease IGBT life more than small changes between high and low temperatures.
Power within alternating current (AC) system is equal to the product of voltage, current, and power factor. Apparent power can be classified as two components, one in phase with the voltage (real power) and the other 90 degrees out of phase with the voltage (reactive power). Real power delivered to a grid is primarily a function of how much power the renewable energy source produces (e.g., proportional to wind speed of the wind or strength of the sun). Reactive power is delivered to control voltage to meet energy storage requirements for system reliability (e.g., of inductances and capacitances in transmission lines, motors, and other devices).
Prior attempts to increase fatigue tolerance within semiconductors are known in the art. For example, many conventional approaches include variations of altering the surfaces of the semiconductor to prolong the life of the device. This approach, however, does not prevent cracks from expanding to critical sizes, for example, which can ultimately lead to fractures.
DE 20 2006 019877 discloses a system for reducing temperature change of semiconductors. The system includes a converter with semiconductors. The converter uses reactive power to reduce a temperature change of the semiconductors. DE 20 2006 019877 does not disclose a temperature regulator in communication that includes a processor, or a peak detector.

SUMMARY OF THE INVENTION

Given the aforementioned deficiencies, a need exists for systems and methods that prolong the life of a semiconductor by preventing crack formations due to drastic temperature changes during switching.
In the present technology, to keep IGBT heat losses from dropping in proportion to reductions in renewable power production, the converter may circulate reactive power within the system such that the net reactive power to or from the grid is unaffected but the current within an IGBT bridge is held more constant. Circulating reactive power keeps current magnitude from dropping in proportion to power. Specifically, the converters operate at a reduced power factor than without circulation of reactive power. A doubly fed induction generator (DFIG) has a topology configured to feed reactive power to the grid directly from the line converter or indirectly by the rotor converter via the generator. Thus, one IGBT bridge can be controlled to output more reactive current and another IGBT bridge can be controlled to absorb the increase.
A system for regulating temperature change of semiconductor components within a converter is herein described but does not form part of the claimed invention. The system includes (i) a temperature regulator in communication with at least one semiconductor within the converter and a power source, and (ii) a peak detector in communication with at least one semiconductor within the converter configured to identify a maximum temperature of each semiconductor. The controller can be configured to execute, through a processor, computer-medium instructions that evaluate the temperature of the semiconductor in which the temperature regulator is in communication.
The peak detector can be further configured to identify a change in temperature calculated as the difference between the maximum temperature of the semiconductor a minimum temperature of the semiconductor when the semiconductor conducts low current.
The controller can be configured to alter the maximum temperature of the at least one semiconductor, using reactive power, to a temperature that increases useful life of the semiconductor.
The controller can calculate a stator reference by adjusting reactive power of the at least one semiconductor such that the at least one semiconductor reaches a predetermined temperature.
The controller can calculate a rotor reference by adjusting reactive power of the at least one semiconductor such that the at least one semiconductor reaches a predetermined temperature.
The controller can calculate a line output reference by adjusting reactive power of the at least one semiconductor such that the at least one semiconductor reaches a predetermined temperature.
The peak detector can include a discharge time sufficient to reach a desired temperature of the semiconductor.
The peak detector can be configured to more accurately identify temperature changes when the semiconductor conducts low current.
In other arrangements, a controller can be configured to alter the maximum temperature of the semiconductor, using a temperature regulator, to a temperature that increases useful life of the semiconductor.
The present invention includes a method according to claim 1 for determining temperature change of a semiconductor component within a converter.
Optional or non-essential features of the method are defined in the sub-claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and form part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the relevant art(s) to make and use the invention.

FIG. 1 is a block diagram illustrating an exemplary application for a variable frequency, in the form of a wind power converter system.
FIG. 2 is a schematic diagram illustrating an inverter in the exemplary application of FIG. 1.
FIG. 3 is a graph representing a mean time to failure of a semiconductor device of FIG. 2 operating at different temperatures.
FIG. 4 is a block diagram of a controller of the data integration systems for FIG. 1.
FIG. 5 is a flow chart illustrating methods associated with the controller of FIG. 4.
FIG. 6 is a block diagram illustrating an exemplary application for a variable frequency, in the form of a solar power converter system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

While the present invention is described herein with illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those skilled in the art with access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the invention would be of significant utility.
Unless defined otherwise, technical and scientific terms used herein have the same meaning as is commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms "first," "second," and the like, as used herein do not denote any order, quantity, or importance, but rather are used to distinguish one element from another. Also, the terms "a" and "an" do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced items. The term "or" is meant to be inclusive and mean either, any, several, or all of the listed items.
The use of "including," "comprising," or "having" and variations thereof herein are meant to encompass the items listed thereafter and equivalents thereof as well as additional items. The terms "connected" and "coupled" are not restricted to physical or mechanical connections or couplings, and can include electrical connections or couplings, whether direct or indirect. The terms "circuit," "circuitry," and "controller" may include either a single component or a plurality of components, which are either active and/or passive components and may be optionally connected or otherwise coupled together to provide the described function.
FIG. 1 depicts an exemplary application in the form of a wind power system 100, suitable for capturing power from wind using turbine blades 102. The system 100 may include a gearbox 110 connected to a turbine rotor 104 of the turbine blades 102. The gearbox 110 adapts the relatively low speed of the turbine rotor 104 with the relatively high speed of a generator 120.
The generator 120 (e.g., an induction generator or synchronous generator) converts the mechanical power into electrical power. For example, the generator 120 illustrated in FIG. 1 may be a doubly fed induction generator (DFIG), which includes a rotor winding 130 and a stator winding 140.
In the illustrated embodiment of FIG. 1, the stator winding 140 is connected to a transformer 115, which transfers electrical power through inductively coupled conductors to a suitable voltage level for an electrical grid. The rotor winding 130 may be connected to the grid by a converter and inverter module (e.g., a converter 150) which decouple mechanical and electrical frequencies (e.g., to enable variable-speed operation).
The converter and inverter module of the system 100 may include two three-phase converters 150. One converter 150 may be connected to the rotor winding 130 and the second converter 150 may be connected to the grid by the transformer 115. The ratio of the voltage produced by the stator winding 140 to the voltage produced by the rotor winding 130 known as the S-R ratio, can be used to determine qualitative factors about the converters 150, such as, but not limited to, temperature within the converter.
FIG. 2 is an example configuration of the converter 150 including one or more semiconductors. The converter 150 may include a plurality of IGBTs 152 and power diodes 154, each diode 154 being antiparallel to a respective IGBT 152. Each IGBT 152 and diode 154 are joined to positive or negative DC lines and output lines I, II, or III with bond wires 156. As seen in the example topology of FIG. 2, the output lines I, II, and III may output three-phase voltages v_I, v_II, and v_III. Changes to the output current of the IGBTs 152, used to produce a three-phase output current waveform at the output 158, can result in power losses, resulting in a higher junction temperature at the IGBTs 152. Such junction temperatures may result in mechanical strain and/or deformation of the bond wires 156, shortening the lifespan of the converters 150.
Cumulative damage (C), due to extreme high or low temperatures, determines semiconductor failure based on the number of thermal cycles and can be defined by the relationship $C = \frac{n_{1}}{N_{1}} + \frac{n_{2}}{N_{2}} + \dots + \frac{n_{i}}{N_{i}},$
where n_i is the number of cycles at the i^th stress level and Ni is the number of cycles to failure at the i^th stress level.
FIG. 3 is a graph illustrating a semiconductor lifetime curve where change in temperature of the semiconductor device from ON to OFF is shown along the x-axis. The number of cycles until failure is shown along the y-axis.
As seen in FIG. 3, reduction in a temperature change (ΔT) by approximately 10 °C improves the semiconductor life by a factor of two. For example, changing the ΔT from 80 °C to 70 °C improves the life from under 100,000 cycles to nearly 200,000 cycles. Similarly, reducing the ΔT from 70 °C to 60 °C improves the life from about 200,000 cycles to more than 400,000 cycles.
Referring back to FIG. 1, to assist in the regulation of ΔT within the converters 150, the system 100 can include additional components, such as a peak detector 170 and a temperature regulator 180, to control one or more operations of the converters 150.
The peak detector 170 can be implemented as a series connection of a diode and a capacitor (not shown) outputting a direct current (DC) voltage equal to the peak value of an applied alternating current (AC) signal. An AC voltage source applied to the peak detector 170 charges the capacitor to the peak of the input. The diode conducts positive "half cycles," charging the capacitor to the waveform peak. When the input waveform falls below the DC "peak" stored on the capacitor, the diode is reverse biased, blocking current flow from capacitor back to the source. Thus, the capacitor retains the peak value even as the waveform drops to zero.
The peak detector 170 can perform automatic measurements on multiple channels approximately simultaneously. The resultant measurements can be used to show data (e.g., plot in graphical form) or transfer the data to another program for alternate use (e.g., transferred to another program). The peak detector 170 can also detect positive peaks (e.g., maximum wavelength heights) or negative peaks (e.g., minimum wave height). The peak detector 170 is described in further detail below, in association with FIG. 5.
The temperature regulator 180 attenuates temperature variations within the converter(s) 150. Circulating reactive power, measured in VARs, through the system keeps the IGBTs 152 from cooling down too much when the power source diminishes.
Circulation of reactive power can continue while rotation of the turbine rotor 104 is within a predetermined operation speed range of the turbine (e.g., manufacturer recommended operating speed). To continue operating the IGBTs 152 after speed of the turbine rotor 104 has been reduced, reactive power can be circulated through AC line filters to facilitate continued switching of the IGBTs 152.
The converter may circulate reactive power within the system such that the current within an IGBT bridge within the converter 150 is constant. Specifically, the converter 150 operates at a reduced power factor, allowing the IGBT bridge to output more reactive current.
In some embodiments, when the speed of the turbine rotor 104 exceeds a normal operating range, additional regulation components, such as fans, heaters, and pumps (not shown), in conjunction with the temperature regulator 180, allow temperature of a coolant to rise. As the coolant temperature rises when the power source disappears, reactive power circulation can be reduced and ultimately de-energized. In this situation, heaters can be used to increase the temperature of the coolant. Alternately, pump speed can be adjusted and/or operation of an anti-condensation system can be used to increase the temperature of the coolant.
In another embodiment, reactive power can be circulated through the AC line filter to keep the IGBTs 152 switching between predetermined ON/OFF positions. For example, in a solar inverter, or a full-power conversion wind turbine converter, when the power source disappears, the IGBTs 152 can be operated at low current, by thermal energy produced by the IGBTs 152 during switching (i.e., switching losses due to heat). Operating the IGBTs 152 instead of shutting them down minimizes temperature reductions in the IGBTs 152 as the power diminishes. While the IGBTs 152 continue switching, the cooling fan speed can be reduced by a cooling fan control. Alternatively, it can be stopped completely to allow the coolant temperature to rise. When the coolant temperature reaches a desired temperature, the regulation components (e.g., the heaters, fans, pumps) can be de-energized.
In some embodiments, the temperature regulator 180 and/or the other regulation components (e.g., cooling fans and/or heaters), can be operated via one or more controllers, such as a controller 400 described in association with FIG. 4 below.
The controller 400 can include a processor to monitor the reactive power output by the converter 150 on the grid side and determine whether the power output by the converter 150 on the grid side meets the reactive power required by the grid. The controller 400 also includes a memory 410. The memory 410 is configurable for storing several categories of software, firmware, and data including, applications 420, a database 430, an operating system (OS) 440, and I/O device drivers 450.
As will be appreciated by those skilled in the art, the OS 440 can be any operating system for use with a data processing system. The I/O device drivers 450 can include various routines accessed through the OS 440 by the applications 420 to communicate with devices, and certain memory components.
The applications 420 can be stored in the memory 410 and/or in a firmware (not shown) as executable instructions and can be executed by a processor 460.
The applications 420 include various programs, such as an iterative temperature sequence 502 that, when executed by the processor 460, process data received into the temperature regulator 180.
The applications 420 may be applied to data stored in the database 430, such as the specified parameters, along with data, e.g., received via the I/O data ports 470. The database 430 represents the static and dynamic data used by the applications 420, the OS 440, the I/O device drivers 450 and other software programs that may reside in the memory 410.
While the memory 410 is illustrated as residing proximate the processor 460, it should be understood that at least a portion of the memory 410 can be a remotely accessed storage system, for example, a server on a communication network. The communications network can include a local area network (LAN), a metropolitan area network (MAN), or a wide area network (WAN), for example.
It should be understood that FIG. 4 and the description above are intended to provide a brief, general description of a suitable environment in which the various aspects of some embodiments of the present disclosure can be implemented. While the description refers to computer-readable instructions, embodiments of the present disclosure can also be implemented in combination with other program modules and/or as a combination of hardware and software in addition to, or instead of, computer readable instructions.
FIG. 5 is a flow chart illustrating an exemplarily application executed by the controller 400. The application can be configured to execute an iterative temperature sequence 502, to determine whether the temperature of the IGBT 152 (seen in FIG. 2) is within a predetermined temperature range. If the IGBT 152 is within the predetermined temperature range, the iterative temperature sequence 502 repeats. However, if the IGBT 152 is not within the predetermined temperature range, reactive power, determined by a reactive power sequence 504 can be circulated through the converter(s) 150.
It should be understood that the steps of the exemplarily application are not necessarily presented in any particular order and that performance of some or all the steps in an alternative order, is possible and is contemplated.
The software may be engaged through the controller 400 communicating an "engage response mode" instruction message through an interface, which sends the initial request to measure a starting temperature of the IGBT 152 within the converter 150, as depicted in the iterative temperature sequence 502.
The sequence 502 begins when the controller 400 measures a starting temperature, T₁, of one or more IGBTs 152 within the converter at step 510. The starting temperature of the IGBT can be measured through any known measuring device such as, but not limited to, thermometers and gauges.
The sequence 502 continues with the controller 400 determining a reference temperature, T_ref, a desired value for the IGBT temperature, at step 515.
In one embodiment, T_ref can be measured using the peak detector 170. The peak detector 170 can be configured to determine a maximum temperature when the IGBT 152 conducts high current and a minimum temperature when the IGBT 152 conducts low current. The peak detector 170 may include a capacitor discharge rate that is gradual, also known as a slow-decay. Additionally, long periods of operation of the converter(s) 150 at a light load may also cause the slow-decay. The discharge rate includes a discharge time sufficient to reach a desired temperature. Since heating of the IGBT 152 is a byproduct of the converter load, T_ref can be a maximum or minimum (peak) temperature point resulting from operation of the converter(s) 150.
The iterative temperature sequence 502 sums the starting temperature T₁ from step 510 with T_ref determined at step 515, to generate a summed temperature, T_sum, at step 520. For example, during the initial temperature sequence, the summed temperature can be expressed as $T_{sum} = T_{1} + T_{ref}$
where T₁ is the starting temperature. In subsequent sequence iterations, the summed temperature can be expressed as $T_{sum} = T_{2, \dots, n} + T_{ref}$
where T₂ is a first adjusted temperature of the IGBT 152 within the iteration sequence 502 and T_n is the temperature associated with an "n^th" iteration of the reactive power sequence 506.
The temperature difference (ΔT), between T_sum and the temperature of the coolant (T_coolant), is calculated at step 525. Also determined within the iterative temperature sequence 502 is whether ΔT is within a predetermined range, at step 530. The predetermined range is such that the life of the IGBT 152 will reduce failure due to temperature related failures as described above. For example, ΔT may be a value of 10 °C.
Where ΔT is within the predetermined range (e.g., path 532), the controller 400 can return to step 510 were the temperature of the IGBT 152 is measured.
Where ΔT is not within the predetermined range (e.g., path 534), the controller 400 can initiate the reactive power sequence 504. Within the reactive power sequence 504, the controller 400 calculates a stator reference modifier (stator modifier, M_stat), a rotor converter current modifier (rotor modifier, M_rot), and a line output converter current modifier (line modifier, M_line).
The controller 400 determines the stator modifier, M_stat, at step 540. Where the IGBT 152 temperature is lower than T_ref, the controller 400 will move the stator reactive current reference to become larger in magnitude. Where the IGBT 152 temperature is higher than T_ref, the regulator will move the stator reactive current reference to lessen the previous increase in magnitude. Specifically, the stator modifier is calculated as $M_{stat} = T_{ref} / T_{1, \dots, n} .$
At step 545, the controller 400 calculates the rotor modifier M_rot based on the stator reference modifier determined in step 550. For example: $M_{rot} = M_{stat} \cdot S - R ratio$
where the S-R ratio is the ratio of the stator winding 140 to the rotor winding 130 within the generator 120.
At step 550, the controller 400 calculates the line modifier, M_line, as the inverse of the rotor modifier for purposes of maintaining a desired net reactive current produced to the grid. Specifically, $M_{line} = (- 1) \cdot M_{rot} .$
M_stat, M_rot, and/or M_line can be communicated by the temperature regulator 180 to component (e.g., converter controls) within the power systems 100 to adjust the speed of the turbine rotor 104. Where the temperature regulator 180 raises the temperature of the IGBT 152, M_stat, M_rot, and M_line adjust as to make each modifier larger in magnitude, while keeping the sum of stator and line reactive currents constant.
The reactive power can circulate through AC line filters within the system 100 until a shut off event occurs. A shut off event may be any event that is predetermined to stop the flow of reactive power. For example, a predetermined passage of time or a predetermined amount of VARs have been transferred to the power system 100 can constitute shut off events. When a shut off event has occurred, reactive power will cease and the controller 400 will measure the reactive power effect on the temperature of the IGBT. Specifically, measuring an adjusted temperature, T₂ at step 510.
The controller 400 can execute the reactive power sequence 504 and the iteration sequence until the ΔT is within the predetermined range. For example, controller 400 can include up to "n" iterations.
Alternate forms of renewable energy, such as a solar power system 101, depicted in FIG. 6 could utilize several embodiments of the disclosed invention. In these embodiments, solar energy is converted into electrical energy through the use of a battery 190 in connection with the converter 150.
The system 101 can additionally contain a charge controller 195 to regulate the rate at which current is added to or drawn from the battery 190. AC and/or DC isolation devices (not shown). Isolation devices allow disconnection of the solar power source (e.g., solar panel) in events such as electrical fault or device maintenance servicing. 502 is whether ΔT is within a predetermined range, at step 530. The predetermined range is such that the life of the IGBT 152 will reduce failure due to temperature related failures as described above. For example, ΔT may be a value of 10 °C.
Where ΔT is within the predetermined range (e.g., path 532), the controller 400 can return to step 510 were the temperature of the IGBT 152 is measured.
Where ΔT is not within the predetermined range (e.g., path 534), the controller 400 can initiate the reactive power sequence 504. Within the reactive power sequence 504, the controller 400 calculates a stator reference modifier (stator modifier, M_stat), a rotor converter current modifier (rotor modifier, M_rot), and a line output converter current modifier (line modifier, Mime).
The controller 400 determines the stator modifier, M_stat, at step 540. Where the IGBT 152 temperature is lower than T_ref, the controller 400 will move the stator reactive current reference to become larger in magnitude. Where the IGBT 152 temperature is higher than T_ref, the regulator will move the stator reactive current reference to lessen the previous increase in magnitude. Specifically, the stator modifier is calculated as $M_{stat} = T_{ref} / T_{1, \dots, n} .$
At step 545, the controller 400 calculates the rotor modifier M_rot based on the stator reference modifier determined in step 550. For example: $M_{rot} = M_{stat} \cdot S - R ratio$
where the S-R ratio is the ratio of the stator winding 140 to the rotor winding 130 within the generator 120.
At step 550, the controller 400 calculates the line modifier, M_line, as the inverse of the rotor modifier for purposes of maintaining a desired net reactive current produced to the grid. Specifically, $M_{line} = (- 1) \cdot M_{rot} .$
M_stat, M_rot, and/or M_line can be communicated by the temperature regulator 180 to component (e.g., converter controls) within the power systems 100 to adjust the speed of the turbine rotor 104. Where the temperature regulator 180 raises the temperature of the IGBT 152, M_stat, M_rot, and M_line adjust as to make each modifier larger in magnitude, while keeping the sum of stator and line reactive currents constant.
The reactive power can circulate through AC line filters within the system 100 until a shut off event occurs. A shut off event may be any event that is predetermined to stop the flow of reactive power. For example, a predetermined passage of time or a predetermined amount of VARs have been transferred to the power system 100 can constitute shut off events. When a shut off event has occurred, reactive power will cease and the controller 400 will measure the reactive power effect on the temperature of the IGBT. Specifically, measuring an adjusted temperature, T₂ at step 510.
The controller 400 can execute the reactive power sequence 504 and the iteration sequence until the ΔT is within the predetermined range. For example, controller 400 can include up to "n" iterations.
Alternate forms of renewable energy, such as a solar power system 101, depicted in FIG. 6 could utilize several embodiments of the disclosed invention. In these embodiments, solar energy is converted into electrical energy through the use of a battery 190 in connection with the converter 150.
The system 101 can additionally contain a charge controller 195 to regulate the rate at which current is added to or drawn from the battery 190. AC and/or DC isolation devices (not shown). Isolation devices allow disconnection of the solar power source (e.g., solar panel) in events such as electrical fault or device maintenance servicing.
It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended claims in any way.

Claims

A method for determining temperature change of semiconductors (152) within a converter (150), the method comprising:
measuring, by a temperature regulator (180) including a processor (400), a first semiconductor temperature at a junction located on a semiconductor (152);

determining, by the processor (400), a reference temperature, using a peak detector (170) configured to determine a maximum temperature when at least one semiconductor (152) conducts high current, and a minimum temperature when the at least one semiconductor (152) conducts low current;

summing, by the processor (400), the first semiconductor temperature and the reference temperature to generate a first temperature sum;

comparing, by the processor (400), the first temperature sum to a coolant temperature to generate a first temperature difference; and

circulating reactive power such that the first temperature difference is adjusted according to an amount of energy sent to the converter (150) by a power source (120), so that the first temperature difference is within a predetermined temperature range.
A method according to claim 1, further comprising:
calculating, by the processor (400), one or more of a stator reference, a rotor reference, and a line output reference by adjusting the reactive power of the at least one semiconductor (152) such that the at least one semiconductor (152) reaches a predetermined temperature; and

using the one or more of the stator reference, the rotor reference, or the line output reference to adjust the power source (120), e.g., by adjusting a turbine rotor (102) of a wind power system (100), to alter the energy to the at least one semiconductor (152).
A method according to claim 1 or claim 2, further comprising:
adjusting the first semiconductor temperature to generate a second semiconductor temperature;

summing, by the processor (400), the second semiconductor temperature and the reference temperature to generate a second temperature sum;

comparing, by the processor (400), the second temperature sum to a coolant temperature to generate a second temperature difference; and

circulating reactive power such that the second temperature difference is adjusted according to an amount of energy sent to the converter (150) by the power source (120).
A method according to claim 3, wherein the reactive power is disengaged by an event, predetermined within the temperature regulator (180).
A method according to any preceding claim, further comprising:
iterating, by the processor (400), the first semiconductor temperature to generate a final semiconductor temperature, by circulating reactive power, such that the final semiconductor temperature is adjusted according to the power sent to the converter (150) by the power source (120).